Adenine-N-Oxide Produced from Adenine with Gamma-Rays and Its Binding to SH Protein

Abstract

¹⁴C-labeled adenine aqueous solution was irradiated with ⁶⁰Co gamma-rays. The yield of adenine-7-N-oxide, a radiolytic product, was determined by Sephadex G-10 column chromatography and TLC autoradiography. The apparent productive yield was very low, but the true yield should be much higher because of the reversible reaction to adenine and the easy decomposition of the N-oxide itself. Using synthesized ¹⁴C-adenine-7-N-oxide, noncovalent binding of this N-oxide to urease, an SH protein, was confirmed in comparison between the presence and absence of SDS by Ultrogel AcA 22 column chromatography. The noncovalent binding of the gamma-irradiated ³⁵S-cysteine was also observed. The yield reached a limit in O₂ easier than in N₂ as the atmosphere for DNA irradiation. These results support an interaction structure, ?? N-O---H-S-, for noncovalent binding which may be applied to the biological system as a radiation-induced damage.